The Levator Veli Palatini Muscle in Cleft Palate Anatomy and Its Implications for Assessing Velopharyngeal Function: A Literature Review Seunghee Ha* Department of Audiology & Speech Pathology, University of Tennessee at Knoxville Background & Objectives: The levator veli palatini (LVP) muscle is most commonly reported as the most abnormal muscle in the population with cleft palate and the muscle plays a significant role in velar elevation, and therefore speech production. Methods: This article reviewed the literature focusing on anatomic aspects of the LVP muscle in normal and cleft palate populations and addressed the significant implication of the studies in clinical services for individuals with cleft palate. Results & Conclusion: Literature addressed that abnormal location and volume of the LVP muscle is closely related to velopharyngeal insufficiency and a complete evaluation of the LVP muscle along with the velopharyngeal mechanism is required to provide the most appropriate and effective treatments to individuals with cleft palate. Continuous improvements of MRI technique lead to effective identification of LVP muscle structures and better clinical decision-making for surgical procedures and speech therapy in individuals with cleft palate. (Korean Journal of Communication Disorders 2007;12;77-89) Key Words: levator veli palatini muscle, anatomic aspects, cleft palate, MRI Ⅰ. Introduction to improve the speech problems. There are several possible factors to account for surgical failure and residual velopharyngeal In individuals with repaired cleft palate, insufficiency. Gross anatomic abnormalities it is estimated that 10 % to 25 % have residual and severity of the cleft in patients are closely velopharyngeal insufficiency (Bradley, 1997; related to surgical failure. The abnormal Marrinan, LaBrie & Mulliken, 1998; Witt & velopharyngeal muscle structures which Marsh, 1997). Individuals with residual velo- remain even after primary palatoplasty may pharyngeal insufficiency show persistent be another significant factor. In particular, nasalized speech and abnormal articulation the levator veli palatini (LVP) muscle plays a patterns. As a result, secondary surgical significant role in velar elevation and it is management or speech therapy is necessary Received January 19, 2007; final revision received February 20, 2007; accepted February 22, 2007. * Correspondence to Seunghee Ha, PhD, Department of Audiology & Speech Pathology, University of Tennessee at Knoxville, USA, e-mail: [email protected], tel.: +1 865 974 4802 ⓒ 2007 The Korean Academy of Speech-Language Pathology and Audiology http://www.kasa1986.or.kr 77 Korean Journal of Communication Disorders 2007;12;77-89 most commonly reported as the most ab- the velopharyngeal muscles shows that normal muscle in the population with cleft sufficient muscle volume of the LVP and its palate. Therefore, the LVP muscle is of great inserted position relative to the soft palate are clinical and research interest. An under- crucial factors to determine velopharyngeal standing of anatomic and physiologic char- competence for speech and swallowing acteristics of the LVP muscle would (Dickson, 1972; Hoopes et al., 1970). contribute to better clinical managements in <Figure - 1> shows the LVP muscle in population with cleft palate. Information relation to the palate, auditory tube, pharynx obtained utilizing videofluoroscopy and and other muscles in a normal newborn. The videoendoscopy techniques which are LVP muscle originates from the lower commonly used for evaluation of the velo- surface of the petrous portion of the temporal pharyngeal mechanism has limited usefulness bone and courses along the surface under the because of the relative inaccessibility of auditory tube. The muscle descends and detailed muscle structures. Recent technical inserts into the soft palate where it blends advancements of instrumental evaluation with levator fibers from the opposite site such as MRI expand our understanding of the (Kuehn & Moon, 2005). The LVP muscle LVP muscle in normal and abnormal has a broad insertion extending into the anatomy and furthermore, make it possible to middle and posterior third of the soft palate identify normal/abnormal distribution and (Boorman & Sommerlad, 1985; Dickson et quantity of the LVP muscle. The purpose of al., 1974; Huang, Lee & Rajendran, 1998; this study is to review literature focusing on Kuehn & Kahane, 1990). In the normal anatomic aspects of the LVP muscle using a mechanism, no muscle tissue attaches variety of techniques and to address the directly to the hard palate (Dickson, 1972; clinical implication of the LVP muscle in Kuehn & Kahane, 1990). The paired levator assessment and treatment of population with muscles form a muscular sling effectively to cleft palate. serve velar elevation. In particular, the angle of the inserting LVP muscle allows the velum to be pulled along a superior and Ⅱ. Anatomy of the Levator posterior path that may be linear or somewhat curved (Kent, Carney & Severeid, 1974; Veli Palatini Muscle Kuehn, 1976). Huang, Lee & Rajendran (1998) observed the LVP and other velo- pharyngeal muscles in 18 fresh cadaveric 1. LVP Muscle in the Normal specimens of normal adults. They reported Anatomy that the LVP muscle forms a muscular sling and its muscle fibers occupy the middle 50 Normal speech production and swal- percent of the velar length measured from the lowing require velar movement, which posterior nasal spine to the tip of the uvula. results in coupling and decoupling of the They also reported that the fibers of each oral and nasal cavities. The LVP muscle is muscle bundle of the levator lay in a the primary muscle responsible for velar transverse orientation without significant elevation during speech and swallowing. overlap across the midline even though this is Most anatomic investigations of the velo- in contrast to the findings of Kuehn & Moon pharyngeal muscles have been conducted (2005). In their histologic study, Kuehn & using dissection and histological techniques. Moon (2005) found that levator fibers cross Literature on normal / abnormal anatomy of the midline to mingle with levator fibers on 78 Ha / The Levator Veli Palatini Muscle in Cleft Palate Anatomy and Its Implications for Assessing Velopharyngeal Function the opposite side. Anteriorly, the levator electromyographic and cinematographic muscle is attached to the posterior margin of analyses conducted by Bell-Berti (1976) and the aponeurosis of the tensor veli palatini Honjo, Harada & Kumazawa (1976), and with overlap on its oral surface medially. nasoendoscopic analyses by Lavorato and Huang, Lee & Rajendran (1998) confirmed Lindholm (1977). Counter evidence indicating that the LVP muscle is well placed to function that the levator muscle may not be as the primary mover in velar elevation. responsible for the lateral pharyngeal wall movement, at least at the level of the hard palate, was provided by Iglesias, Kuehn & Morris (1980). However, using rapid MRI technique Yamawaki, Nishimura & Suzuki (1999) reported that the LVP muscle contraction contributes to the lateral pha- ryngeal wall movement on phonation. In their study the transverse plane of rapid MRI indicated that medial movement of the lateral pharyngeal walls was coincident with inward displacement of the eustachian tube cartilage, which was caused by contraction of the LVP muscle. The level of this movement was clearly shown in the plane 5mm lateral to the mid-sagittal plane on rapid MRI. This sagittal plane could display the actual side of medial movement of the lateral pharyngeal wall and could not be obtained by <Figure - 1> Superolateral view of the palate other methods of imaging such as multiview and pharynx showing the LVP muscle and other muscles in a normal newborn. Arrows fluoroscopy and radiography. Yamawaki, indicate the LVP muscle sling (Millard, 1980). Nishimura & Suzuki (1999) showed that MRI information of serial changes within a In addition to velar elevation, some short period has great potential to shed light researchers have presented evidence that the on anatomic and physiologic features of the LVP muscle plays a role in lateral pharyngeal velopharyngeal mechanism, for which other wall movement for normal velopharyngeal techniques have limitations. closure for speech (Beery, Rood & Schramm, 1983; Bell-Berti, 1976; Honjo, Harada & 2. LVP Muscle in the Population with Kumazawa, 1976; Lavorato & Lindholm, 1977; Cleft Palate Yamawaki, Nishimura & Suzuki, 1999; Ysunza et al., 1999). Although there is con- Cleft palate anatomy has been well troversy about which muscle is responsible for described in the literature (Dickson, 1972; lateral pharyngeal wall movement during Latham, Long & Latham, 1980; Maue-Dickson speech, several investigators have argued & Dickson, 1980). Some studies recorded that the LVP muscle contributes to mesial anatomical findings in cleft palates at the movement of the lateral wall component of time of intraoperative muscle dissection normal velopharyngeal closure. These studies in patients undergoing cleft palate repairs have included various techniques such as (Koch, Grzonka & Koch, 1998, 1999; 79 Korean Journal of Communication Disorders 2007;12;77-89 Mehendale, 2004; Sommerlad et al., 1994, course and insertion of the LVP muscle is 2002). Latham, Long & Latham (1980) markedly abnormal. <Figure - 2> illustrates demonstrated convergence of the fibers of a superolateral view of the palate and the LVP, palatopharyngeus, and uvulus pharynx, showing the position